refactor(curve25519): split the single file curve25519.c into multiple files for better readability

Signed-off-by: Praneeth Sarode <praneethsarode@gmail.com>
Reviewed-by: Jakub Jelen <jjelen@redhat.com>

src/curve25519_crypto.c

@@ -0,0 +1,158 @@
+/*
+ * curve25519_crypto.c - Curve25519 ECDH functions for key exchange (OpenSSL)
+ *
+ * This file is part of the SSH Library
+ *
+ * Copyright (c) 2013-2023 by Aris Adamantiadis <aris@badcode.be>
+ *
+ * The SSH Library is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, version 2.1 of the License.
+ *
+ * The SSH Library is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+ * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
+ * License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with the SSH Library; see the file COPYING.  If not, write to
+ * the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
+ * MA 02111-1307, USA.
+ */
+
+#include "config.h"
+#include "libssh/curve25519.h"
+
+#include "libssh/crypto.h"
+#include "libssh/priv.h"
+#include "libssh/session.h"
+
+#include <openssl/err.h>
+#include <openssl/evp.h>
+
+int ssh_curve25519_init(ssh_session session)
+{
+    ssh_curve25519_pubkey *pubkey_loc = NULL;
+    EVP_PKEY_CTX *pctx = NULL;
+    EVP_PKEY *pkey = NULL;
+    size_t pubkey_len = CURVE25519_PUBKEY_SIZE;
+    int rc;
+
+    if (session->server) {
+        pubkey_loc = &session->next_crypto->curve25519_server_pubkey;
+    } else {
+        pubkey_loc = &session->next_crypto->curve25519_client_pubkey;
+    }
+
+    pctx = EVP_PKEY_CTX_new_id(EVP_PKEY_X25519, NULL);
+    if (pctx == NULL) {
+        SSH_LOG(SSH_LOG_TRACE,
+                "Failed to initialize X25519 context: %s",
+                ERR_error_string(ERR_get_error(), NULL));
+        return SSH_ERROR;
+    }
+
+    rc = EVP_PKEY_keygen_init(pctx);
+    if (rc != 1) {
+        SSH_LOG(SSH_LOG_TRACE,
+                "Failed to initialize X25519 keygen: %s",
+                ERR_error_string(ERR_get_error(), NULL));
+        EVP_PKEY_CTX_free(pctx);
+        return SSH_ERROR;
+    }
+
+    rc = EVP_PKEY_keygen(pctx, &pkey);
+    EVP_PKEY_CTX_free(pctx);
+    if (rc != 1) {
+        SSH_LOG(SSH_LOG_TRACE,
+                "Failed to generate X25519 keys: %s",
+                ERR_error_string(ERR_get_error(), NULL));
+        return SSH_ERROR;
+    }
+
+    rc = EVP_PKEY_get_raw_public_key(pkey, *pubkey_loc, &pubkey_len);
+    if (rc != 1) {
+        SSH_LOG(SSH_LOG_TRACE,
+                "Failed to get X25519 raw public key: %s",
+                ERR_error_string(ERR_get_error(), NULL));
+        EVP_PKEY_free(pkey);
+        return SSH_ERROR;
+    }
+
+    session->next_crypto->curve25519_privkey = pkey;
+    pkey = NULL;
+
+    return SSH_OK;
+}
+
+int curve25519_do_create_k(ssh_session session, ssh_curve25519_pubkey k)
+{
+    ssh_curve25519_pubkey *peer_pubkey_loc = NULL;
+    int rc, ret = SSH_ERROR;
+    EVP_PKEY_CTX *pctx = NULL;
+    EVP_PKEY *pkey = NULL, *pubkey = NULL;
+    size_t shared_key_len = CURVE25519_PUBKEY_SIZE;
+
+    if (session->server) {
+        peer_pubkey_loc = &session->next_crypto->curve25519_client_pubkey;
+    } else {
+        peer_pubkey_loc = &session->next_crypto->curve25519_server_pubkey;
+    }
+
+    pkey = session->next_crypto->curve25519_privkey;
+    if (pkey == NULL) {
+        SSH_LOG(SSH_LOG_TRACE,
+                "Failed to create X25519 EVP_PKEY: %s",
+                ERR_error_string(ERR_get_error(), NULL));
+        return SSH_ERROR;
+    }
+
+    pctx = EVP_PKEY_CTX_new(pkey, NULL);
+    if (pctx == NULL) {
+        SSH_LOG(SSH_LOG_TRACE,
+                "Failed to initialize X25519 context: %s",
+                ERR_error_string(ERR_get_error(), NULL));
+        goto out;
+    }
+
+    rc = EVP_PKEY_derive_init(pctx);
+    if (rc != 1) {
+        SSH_LOG(SSH_LOG_TRACE,
+                "Failed to initialize X25519 key derivation: %s",
+                ERR_error_string(ERR_get_error(), NULL));
+        goto out;
+    }
+
+    pubkey = EVP_PKEY_new_raw_public_key(EVP_PKEY_X25519,
+                                         NULL,
+                                         *peer_pubkey_loc,
+                                         CURVE25519_PUBKEY_SIZE);
+    if (pubkey == NULL) {
+        SSH_LOG(SSH_LOG_TRACE,
+                "Failed to create X25519 public key EVP_PKEY: %s",
+                ERR_error_string(ERR_get_error(), NULL));
+        goto out;
+    }
+
+    rc = EVP_PKEY_derive_set_peer(pctx, pubkey);
+    if (rc != 1) {
+        SSH_LOG(SSH_LOG_TRACE,
+                "Failed to set peer X25519 public key: %s",
+                ERR_error_string(ERR_get_error(), NULL));
+        goto out;
+    }
+
+    rc = EVP_PKEY_derive(pctx, k, &shared_key_len);
+    if (rc != 1) {
+        SSH_LOG(SSH_LOG_TRACE,
+                "Failed to derive X25519 shared secret: %s",
+                ERR_error_string(ERR_get_error(), NULL));
+        goto out;
+    }
+    ret = SSH_OK;
+
+out:
+    EVP_PKEY_free(pubkey);
+    EVP_PKEY_CTX_free(pctx);
+    return ret;
+}